Lower GI 2017

Adaptive RT: choosing the adaptive scheme

Applying LQ model including repopulation:

BED = nd (1 + d/ α / β ) - γ / α (T – Tk)

- Original scheme:

where: d, daily dose, n n ° fractions, γ / α repopulation factor (0.6Gy/day), Tk delay time (7 days), α / β =10 (Widder et al, 2005)

- Adaptive scheme:

BED = md (1 + d/ α / β ) + (n-m)d adapt (1 + d adapt / α / β ) - γ / α (T – Tk)

Assessing m and d adapt to escalate the boost dose to EQD2=54Gy

- - Practical limitations:

imaging for adaptive boosting not before half-RT

Leaving time for image matching, re-contouring, re-planning, scheduling….